Documents disponibles écrits par cet auteur

Improved efficiency of dye-sensitized solar cells using a vertically aligned carbon nanotube counter electrode / Robert A. Sayer in Transactions of the ASME. Journal of solar energy engineering, Vol. 132 N° 2 (Mai 2010) 

Public ISBD [article]  in Transactions of the ASME. Journal of solar energy engineering > Vol. 132 N° 2 (Mai 2010) . - pp. [021007/1-4] Titre : Improved efficiency of dye-sensitized solar cells using a vertically aligned carbon nanotube counter electrode Type de document : texte imprimé Auteurs : Robert A. Sayer, Auteur ; Stephen L. Hodson, Auteur ; Timothy S. Fisher, Auteur Année de publication : 2011 Article en page(s) : pp. [021007/1-4] Note générale : Energie Solaire Langues : Anglais (eng) Mots-clés : Carbon  nanotubes  Electrochemical  electrodes  Plasma  CVD  Solar  cells Index. décimale : 621.47 Résumé : Dye-sensitized solar cells (DSSCs) offer many advantages in comparison to their Si-based counterparts, including lower cost of raw materials, faster manufacturing time, and the ability to be integrated with flexible substrates. Although many advances have been made in DSSC fabrication over recent years, their efficiency remains lower than commercially available Si photovoltaic cells. Here we report improved efficiency of TiO2/anthocyanin dye solar cell using vertically aligned arrays of carbon nanotubes (CNTs) as a counter electrode. Dense vertically oriented CNT arrays are grown directly on the counter electrode using microwave plasma chemical vapor deposition and a trilayer (Ti/Al/Fe) catalyst. The resulting arrays are 30 µm in height and have a number density of approximately 5×108/mm2. By directly growing the CNTs on the counter electrode substrate, electrical interface conductance is enhanced. The performance of both as-grown and N-doped (using a nitrogen plasma) CNT arrays is reported. The fabricated DSSCs are tested under AM1.5 light. Increased short-circuit current is observed in comparison to graphite and Pt counter electrodes. We attribute this improvement to the large surface area created by the 3D structure of the arrays in comparison to the planar geometry of the graphite and Pt electrodes, as well as the excellent electrical properties of the CNTs. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO00013200 [...] [article] Improved efficiency of dye-sensitized solar cells using a vertically aligned carbon nanotube counter electrode [texte imprimé] / Robert A. Sayer, Auteur ; Stephen L. Hodson, Auteur ; Timothy S. Fisher, Auteur . - 2011 . - pp. [021007/1-4]. Energie Solaire Langues : Anglais (eng) in Transactions of the ASME. Journal of solar energy engineering > Vol. 132 N° 2 (Mai 2010) . - pp. [021007/1-4] Mots-clés : Carbon  nanotubes  Electrochemical  electrodes  Plasma  CVD  Solar  cells Index. décimale : 621.47 Résumé : Dye-sensitized solar cells (DSSCs) offer many advantages in comparison to their Si-based counterparts, including lower cost of raw materials, faster manufacturing time, and the ability to be integrated with flexible substrates. Although many advances have been made in DSSC fabrication over recent years, their efficiency remains lower than commercially available Si photovoltaic cells. Here we report improved efficiency of TiO2/anthocyanin dye solar cell using vertically aligned arrays of carbon nanotubes (CNTs) as a counter electrode. Dense vertically oriented CNT arrays are grown directly on the counter electrode using microwave plasma chemical vapor deposition and a trilayer (Ti/Al/Fe) catalyst. The resulting arrays are 30 µm in height and have a number density of approximately 5×108/mm2. By directly growing the CNTs on the counter electrode substrate, electrical interface conductance is enhanced. The performance of both as-grown and N-doped (using a nitrogen plasma) CNT arrays is reported. The fabricated DSSCs are tested under AM1.5 light. Increased short-circuit current is observed in comparison to graphite and Pt counter electrodes. We attribute this improvement to the large surface area created by the 3D structure of the arrays in comparison to the planar geometry of the graphite and Pt electrodes, as well as the excellent electrical properties of the CNTs. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO00013200 [...]

Modeling of polarization-specific phonon transmission through interfaces / Zhen Huang in Journal of heat transfer, Vol. 133 N° 11 (Novembre 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [114502/1-3] Titre : Modeling of polarization-specific phonon transmission through interfaces Type de document : texte imprimé Auteurs : Zhen Huang, Auteur ; Jayathi Y. Murthy, Auteur ; Timothy S. Fisher, Auteur Année de publication : 2012 Article en page(s) : pp. [114502/1-3] Note générale : Physique Langues : Anglais (eng) Mots-clés : Phonon  Green's  function  Polarization-specific  Transmission  function Index. décimale : 536 Chaleur. Thermodynamique Résumé : In this work, the atomistic Green's function method is extended to compute transmission functions for each phonon polarization. The eigenvectors and eigenvalues of the overall density of states matrices are manipulated to yield a density of states matrix for each polarization. A decomposed self-energy is calculated from the density of states matrix for each polarization and used to calculate the transmission function for a particular phonon branch. In a pure bulk material such as silicon, each transmission function exhibits a frequency-independent value of unity. In heterogeneous bulk materials, the transmission function is reduced significantly due to the junction of dissimilar materials. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] Modeling of polarization-specific phonon transmission through interfaces [texte imprimé] / Zhen Huang, Auteur ; Jayathi Y. Murthy, Auteur ; Timothy S. Fisher, Auteur . - 2012 . - pp. [114502/1-3]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [114502/1-3] Mots-clés : Phonon  Green's  function  Polarization-specific  Transmission  function Index. décimale : 536 Chaleur. Thermodynamique Résumé : In this work, the atomistic Green's function method is extended to compute transmission functions for each phonon polarization. The eigenvectors and eigenvalues of the overall density of states matrices are manipulated to yield a density of states matrix for each polarization. A decomposed self-energy is calculated from the density of states matrix for each polarization and used to calculate the transmission function for a particular phonon branch. In a pure bulk material such as silicon, each transmission function exhibits a frequency-independent value of unity. In heterogeneous bulk materials, the transmission function is reduced significantly due to the junction of dissimilar materials. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]

Phonon transport across mesoscopic constrictions / Dhruv Singh in Journal of heat transfer, Vol. 133 N° 4 (Avril 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [042402/1-8] Titre : Phonon transport across mesoscopic constrictions Type de document : texte imprimé Auteurs : Dhruv Singh, Auteur ; Jayathi Y. Murthy, Auteur ; Timothy S. Fisher, Auteur Année de publication : 2011 Article en page(s) : pp. [042402/1-8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Boltzman  transport  equation  Constriction  resistance  Ballistic-diffusive  transition  Gas  gap  conductance  Slip  flow  and  heat  transfer  Knudsen  number  Temperature  jump Index. décimale : 536 Chaleur. Thermodynamique Résumé : Phonon transport across constrictions formed by a nanowire or a nanoparticle on a substrate is studied by a numerical solution of the gray Boltzmann transport equation (BTE) resolving the effects of two length scales that govern problems of practical importance. Predictions of total thermal resistance for wire/substrate and particle/substrate combinations are made for the entire range of Knudsen number, with an emphasis on resolving transport in the mesoscopic regime where ballistic-diffusive mechanisms operate and analytical expressions are not available. The relative magnitudes of bulk and constriction resistance are established, and a correlation for overall thermal resistance spanning the range of practical Knudsen numbers is provided. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Phonon transport across mesoscopic constrictions [texte imprimé] / Dhruv Singh, Auteur ; Jayathi Y. Murthy, Auteur ; Timothy S. Fisher, Auteur . - 2011 . - pp. [042402/1-8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [042402/1-8] Mots-clés : Boltzman  transport  equation  Constriction  resistance  Ballistic-diffusive  transition  Gas  gap  conductance  Slip  flow  and  heat  transfer  Knudsen  number  Temperature  jump Index. décimale : 536 Chaleur. Thermodynamique Résumé : Phonon transport across constrictions formed by a nanowire or a nanoparticle on a substrate is studied by a numerical solution of the gray Boltzmann transport equation (BTE) resolving the effects of two length scales that govern problems of practical importance. Predictions of total thermal resistance for wire/substrate and particle/substrate combinations are made for the entire range of Knudsen number, with an emphasis on resolving transport in the mesoscopic regime where ballistic-diffusive mechanisms operate and analytical expressions are not available. The relative magnitudes of bulk and constriction resistance are established, and a correlation for overall thermal resistance spanning the range of practical Knudsen numbers is provided. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]